It is known from the prior art to operate cutting units equipped with conveyor belts for harvest transport, so called drapers, having a rigid or flexible cutter bar, in at least two operating modes, depending on the harvest conditions. For harvesting grain, the cutting unit is guided over the ground with rigid cutter bars at a preset cutting height, i.e. a predefined height setting. Changes in the distance between the ground and the cutter bar of the cutting unit are reacted to, such that the cutting unit is continuously adjusted in terms of its distance to the ground. For this, the cutting unit has a first sensor assembly, which can be deactivated, that is disposed on the cutting unit, for operating the cutting unit in this first operating mode. The first sensor assembly is formed by numerous sensor arms or bands disposed on the undersurface of the cutting unit, which are disposed directly behind the cutter bar.
A second operating mode is the flexible operation of the cutter bar, which lies on the ground in order to follow the contour of the ground, while the cutting unit frame of the cutting unit is guided at a predefined distance from the ground. For this, the cutting unit comprises a second sensor assembly for operating the cutting unit in the second operating mode.
Switching between these two operating modes requires the deactivation of the first sensor assembly, e.g. by removing the sensor bands or through the manual transferring of the sensor bands into a parking position, and the subsequent calibration of a control device by means of which an actuating element is activated, which maintains a constant spacing between the cutting unit, or cutting unit frame, and the ground. Switching from the first operating mode to the second operating mode and back is time consuming due to the manual deactivation, or activation, respectively, in each case accompanied by an interruption in the operation thereof, and the calibration process that is to be carried out.